- Author
-
Macek, A. J.
|
Semple, J. M.
- Title
- Combustion of Boron Particles at Elevated Pressures. Project SQUID. Technical Report.
- Coporate
- Atlantic Research Corp., Alexandria, VA
- Sponsor
- Purdue Univ., Lafayette, IN
- Report
-
ARC-13-PU,
June 1970,
34 p.
- Distribution
- Available from National Technical Information Service
- Contract
- N00014-67-A-0226-0005
NR-098-038
- Book or Conf
- Combustion Institute, Symposium (International) on Combustion, 13th. August 23-29, 1970,
Combustion Institute, Pittsburgh, PA,
Salt Lake City, UT,
859-868 p.,
1970
- Keywords
-
boron
|
pressure
|
combustion
|
ignition limits
|
droplets
|
burning rate
|
induction period
- Abstract
- Combustion of single boron particles, about 75 mu in diameter from a crystalline powder sample has been studied. Particles were ignited by being dropped through a focused laser beam in several oxidizing gases over a range of pressures. In pure oxygen, in air, and in O2/Ar(20,80), particles were merely preheated to a temperature about 2000 deg K; ignition took place spontaneously after a measurable induction period. Quantitative values of both the induction period and the subsequent self-sustained combustion period are listed. In air and in the O2/Ar mixture the burning times decrease from about 45 msec to about 20 msec as the pressure is increased from 1 to 35 atm. In pure O2 at atmospheric pressure the total burning time is only 6.8 msec. In pure CO2 and in O2/N2(7/93) there is no induction period, no self-ignition, and no steady-state combustion; particles must be brought to a burning regime by an external energy flux, and they are able to maintain that regime for only a limited time before extinguishment. It is shown that the classical theory of ignition and combustion can account for all three observed burning modes: metastable surface reaction during the pre-ignition period, rapid self-sustained diffusion-combustion, and decaying combustion. Previously reported reaction-rate and ignition-limit data are used for quantitative estimates of parameters pertaining to the three regimes.